1. Field of the Invention
The present application is generally related to treating uterine disorders and is more specifically related to systems and methods using balloon catheters for treating uterine disorders.
2. Description of the Related Art
Excessive or abnormal uterine bleeding in premenopausal females, commonly referred to as menorrhagia, has been a leading cause of about 30% of the hysterectomies performed in the United States. Women afflicted with menorrhagia typically lose 10 to 25 times the normal amount of blood during their menstrual cycle and often contend with iron deficiencies, pain, fatigue, and the inability to participate in daily activities. While hysterectomies are effective, less invasive outpatient procedures have been introduced that preserve the uterus and reduce recovery time. One of the newer procedures, commonly referred to as endometrial ablation, involves inserting a balloon filled with a heated fluid into the uterus. In one embodiment of a system sold under the trademark THERMACHOICE by Johnson & Johnson of New Brunswick, N.J., a balloon catheter is inserted into a uterus, and inflated with a 5% dextrose solution. After the balloon is inflated with the solution to a certain pressure, the fluid is heated to a predetermined temperature for a period of time that coagulates, ablates, necroses, or destroys the endometrium layer of the uterus. After the procedure is completed, the fluid is withdrawn from the balloon and the balloon is removed from the uterus. The uterine lining will then shed over a 7-10 day period.
An endometrial ablation procedure requires controlling the temperature and internal temperature of the balloon. Temperature fluctuations and gradients along the surface of the balloon may cause uneven tissue ablation resulting in a less than optimal outcome. Balloon surface temperature fluctuations and gradients are the result of the fluid not mixing fully within the balloon. When the fluid is not completely mixed, the fluid temperature is subject to convection currents of the fluid within the balloon. While cooler fluid moves toward the bottom of the balloon, the warmer, less dense fluid rises. When the fluid within the balloon is subject to such convection during heating, considerable temperature fluctuations along the surface of the balloon may result.
Some balloon catheters circulate fluid by means of separate inlet and outlet passages that connect the balloon with an external heating element. Heat is circulated from the external heating element through the inlet passage into the balloon. Then, the fluid from the balloon is returned to the external heating element through the outlet passage. Such a balloon catheter design requires the hot fluid to pass through the vagina and the opening of the cervix, which may cause physical discomfort or possible tissue damage as heat is conducted through the balloon catheter walls. Since the hot fluid must travel a significant distance between the external heating element and the balloon surface being heated, efficient control over the temperature of the balloon surface is difficult.
Other known heated balloon catheters circulate fluid via a pair of one way valves mounted within a housing located at the end of a fluid delivery tube. The housing is surrounded by an inflatable member, such as a balloon. The first valve permits fluid flow from the housing into the balloon, and the second valve permits flow from the balloon into the housing. The valves respond to alternating pressure differentials between the balloon and the housing created by an external bellows or piston which causes pulses of fluid to move up and down the fluid delivery tube. Such a configuration requires circulating hot fluid from the balloon into the fluid delivery tube, creating a risk of causing discomfort to the patient or vaginal tissue damage.
Mechanical circulation or agitation of fluid within the balloon has been known to improve temperature consistency over the surface of the balloon. For example, commonly assigned U.S. Pat. No. 5,954,714, the disclosure of which is hereby incorporated by reference herein, teaches a device for endometrial ablation procedures including a balloon having an internal heater for heating a fluid to a desired temperature. A rotary impeller is positioned distally of the heater for causing the fluid inside the balloon to move around the balloon. The circulation of the fluid by the rotary impeller eliminates some of the temperature differentials along the surface of the balloon, particularly those portions of the balloon proximate the cornua region of the uterus.
Commonly assigned U.S. Pat. No. 5,891,094, the disclosure of which is hereby incorporated by reference herein, teaches a system for the direct heating of a fluid solution in a hollow body organ. The system includes a distal tip having fluid inflow lumens that direct the fluid into a heating chamber. An impeller is located distally of the heating chamber. As fluid enters the heating chamber from the inflow lumens, it passes by electrodes for heating the fluid and exits the chamber through outlets. The impeller rotates for pulling the fluid into the heating chamber and then discharging the fluid through the outlet for circulation within the uterine cavity.
In spite of the above advances, there remains a need for balloon catheter systems and methods that more accurately and efficiently heat the fluid inside the balloon, that more efficiently monitor and control fluid pressure inside the balloon, that more efficiently circulate fluid throughout the balloon, that more efficiently transfer heat from a heating element to fluid, and that provide more uniform heating of the balloon surface.